04/07/2023 11:23, Gupta, Nipun: > On 7/4/2023 1:36 PM, Ding, Xuan wrote: >> From: Gupta, Nipun <nipun.gu...@amd.com> >>> From: Ding, Xuan <xuan.d...@intel.com> >>>> From: Ding, Xuan >>>>> From: Nipun Gupta <nipun.gu...@amd.com> > >>>>> Hi Xuan, > >>>>> > >>>>> Thanks for pointing out the issue and figuring out the patch which > >>>>> introduced this. If you have answers to below queries, please let me > >>>>> know: > >>>>> > >>>>> Is there any other test cases which tests "--no-huge" which pass? > >>>> > >>>> Yes, there are test cases adding "--no-huge" option to validate 4k > >>>> page size in async vhost. > >>>> Actually, the page size is decided by front-end, so I think this > >>>> case can be removed. > >>>> > >>>> Previously, testpmd can start with "--no-huge" options (not sure if > >>>> there are test cases). > >>>> Cmd: ./build/app/dpdk-testpmd -l 5-6 -n 4 --no-huge -m 1024 -- -i > >>>> > >>>>> > >>>>> Also, if we change the "-m" option to provide lower memory, does > >>>>> the test pass? > >>>> > >>>> "-m" option is also added and does not work. > >>>> > >>>>> > >>>>> When you mention too many pages exceed the capability of IOMMU, > >>>>> you are referring to HW capability to create multiple pages? Here > >>>>> it seems in case of 4K page size we need 256K pages which is limiting > >>>>> the > >> capacity? > >>>> > >>>> Yes, this is the result of my initial debugging. > >>>> The direct impact is that this kind of testpmd cases cannot start now. > >>>> If this is expected, I think we can close this defect and ignore the > >>>> "--no- > >> huge" > >>>> option when start. > >>> > >>> Any insights? Should we just ignore the "--no-huge" option and close this > >> defect? > >>> Now we did this as a workaround. Seems no one uses the "--no-huge" > >>> option in testpmd now. > >> > >> VFIO supports dma_entry_limit as a module parameter, which has a default > >> value of U16_MAX i.e. 64K, most likely which is limiting creation of 256K > >> entries for 4K pages here. This can be modified while inserting vfio > >> module: > >> modprobe vfio_iommu_type1 dma_entry_limit=1000000 > > > > Thanks for your suggestion. I tried it on ubuntu 22.04 but it does not work. > > The reason I think is vfio-pci is build-in in kernel driver (since 20.04) > > and it does not support dynamic insmod/rmmod. > > > > Does this command need to rmmod vfio first and then modprobe again? > > > > If it is inserted as a module then you can remove using rmmod and then > modprobe again with the dma_entry_limit parameter. Also note, > vfio_iommu_type1 is the module which is limiting the entries to 64K, so > this module needs to be inserted again providing the dma_entry_limit > module param. > > In case the module is built-in you can provide via kernel command line > parameter (ref: > https://www.kernel.org/doc/html/v4.12/admin-guide/kernel-parameters.html). > As per this ref document, "vfio_iommu_type1.dma_entry_limit=1000000" > should be used in the bootargs to set the module parameters. > > FYI.. DPDK documentation also mentions the limitation at: > https://doc.dpdk.org/guides/linux_gsg/linux_drivers.html
Yes the parameter is discussed in https://doc.dpdk.org/guides/linux_gsg/linux_drivers.html#vfio-memory-mapping-limits but it does not mention we may need to decrease it with --no-huge. Please could you add this to the documentation?
